1. Technical Field
The present disclosure relates to a wireless power transmission system that transmits power wirelessly, and a power transmission device.
2. Description of the Related Art
As of recent, there has been proposed a technology which transmits electric power wirelessly (noncontact), using a new method called resonant magnetic coupling. For example, in the wireless power transmission system disclosed in U.S. Patent Application Publication No. 2008/0278264, two resonators are magnetically coupled by way of leakage (evanescent tail) of vibration energy generated in space in the perimeter of the resonators (antennas). Such wireless power transmission according to resonant magnetic coupling enables marked increase in the transmission distance, in comparison with conventional methods using electromagnetic inductance. It is said that good energy transmission can be performed in a case where an inter-resonator coupling coefficient k is larger than the root of the product of the attenuation constants Γ1 and Γ2 of the resonators. However, it has been demanded of this conventional art to be able to output a constant voltage to a load and also transmit power with high efficiency, even in cases where the load fluctuates or the environment in the perimeter of the antenna changes.